Facing a drier future, water managers turn to science — The Rio Blanco Herald-Times #ColoradoRiver #COriver #aridification

From the Colorado River District via The Rio Blanco Herald-Times:

A growing body of research shows that the Upper Colorado River Basin is growing warmer on average. In fact, the national hot spot centers on Western Colorado and much of the Southwest.

A result: a significant reduction in the snowpack that makes up the Southwest’s main water supply.

In the Colorado River District’s “Know Your Snow” webinar, Deputy Chief Engineer Dave Kanzer and National Snow and Ice Data Center researcher Jeff Deems explored how water managers and snow scientists are studying and adapting to the changes to our snowpack and water supply.

The “Know Your Snow” webinar is available online at http://www.coloradoriverdistrict.org/events-directory/webinars/ (scan the Zapcode on the photo to the right with your Zappar smartphone app for a direct link.)

About three-quarters of the snowmelt that forms the Colorado River’s flow falls as snow at elevations above 8,500 feet in the mountains of the Upper Colorado Basin, Kanzer explained. Deems pointed out that the 15 Western Slope counties that make up the Colorado River District have warmed at a rate from about 2 degrees Fahrenheit in Summit County to more than 4 degrees in Mesa, Montrose, Ouray and Rio Blanco counties since about the early 1900s, according to data developed by the National Oceanic and Atmospheric Administration.

“We’re seeing changes on the order of 4 or 5 degrees in parts of the District,” Deems said. “This is just a slice out of this big, warming bullseye that is hitting the Upper Colorado (River) Basin over that time period. This is a problem for us because we rely on the snowpack, and that’s because warming reduces stream flow through a number of different mechanisms in this snowmelt-dominated basin.”

That reduction comes from several factors: more snow falling as rain, earlier spring snowmelt, more snow directly evaporating into the atmosphere instead of melting into streams and a longer growing season that has plants taking up more water.

Deems explained that for every 1 degree of warming, there is an estimated 3 to 4% decline in annual runoff. That’s about double the amount of water Las Vegas uses in one year, and 18 months of water supply for the city of Los Angeles, Deems said.

A recent study by the U.S. Geological Survey found that a decline in flow due to warming is even greater than earlier studies have shown, with statistics suggesting that average annual flow decreases by 9.3% for every 1.8 degrees of warming.

All of this poses a threat to drinking water, irrigation to grow our food and water to maintain healthy wildlife habitats. The Colorado River District is not only studying the water-supply risks posed by warming temperatures but also implementing solutions such as cloud seeding to make sure West Slope communities are prepared for future challenges.

Cloud seeding to increase snowpack

As part of an effort to boost snowpack, Kanzer coordinates the Colorado River District’s cloud seeding program. Increasingly, water managers are turning to cloud seeding, a practice that can increase how much snow winter storms produce.

“We’re trying to figure out how to mitigate and adapt to a changing world,” Kanzer said. “We’re doing this through cloud seeding, and (we’re) implementing these programs throughout Western Colorado. In fact, this is going on throughout the West and throughout the world.”

Cloud seeding requires a specific set of conditions to be successful, Kanzer explained. A cloud must contain super-cooled water. Water vapor in these clouds is cold enough to form ice crystals, around 5 to 23 degrees Fahrenheit, but it needs something on which to crystalize. When conditions in a storm system are right, with favorable winds with proper uplift, cloud seeding generators send tiny particles of silver iodide into the moisture-laden clouds, typically using propane-fired burners on the ground.

Silver iodide has been proven to be safe for the environment, Kanzer said, adding that it is effective because and it naturally has a similar crystal structure to the ice crystals that form snowflakes.

The super-cooled liquid water more efficiently freezes on to these introduced tiny particles of silver iodide, building small ice crystals that grow into snowflakes.

Kanzer said cloud seeding could increase snow on the ground by up to 15%, boosting what might have been a 10-inch snowstorm by 1.5 inches. After a successful season of cloud seeding, this might, in turn, lead to as much as a 5% increase in streamflow in watersheds where cloud seeding occurred. This increases recreation opportunities for skiers in the winter and boaters in the warmer months, he added.

“And it helps us with our water supplies, of course, and that’s what we’re really focused on here at the Colorado River District,” Kanzer said.

Improving predictions with better data

While Kanzer’s work focuses on increasing the amount of snowpack, Deems’ research seeks to better understand what snow we have.

He explained that water supply forecasts are traditionally generated by comparing the current amount of snow on the ground at fixed locations to historical streamflow records. With the changes we are experiencing, Deems said these methods of comparing the present to the past are no longer accurate.

Additionally, snowpack is measured by a network of weather stations widely spread out across the mountain landscape where Colorado’s snowfall accumulates. While these stations provide accurate measurements in very specific locations, they don’t indicate how much snow, and how much water, might be stored high in the mountains, above the elevations where these stations are located.

Deems’ company, the Airborne Snow Observatory, uses a system called light detection and ranging — LIDAR for short — to measure snow across the entire landscape. From a plane, Deems’ team sends pulses of scanning laser light toward the earth, which reflect off the snow. Researchers can then use information in the reflection to build a three-dimensional picture of the snowscape.

This technology gives snow scientists and water planners landscape-based information about how much snow, and water, is present. This technology is detailed enough to reveal the deep pockets of snow below bare slopes where avalanches occurred or even areas where snowmaking was used to make terrain parks on a ski run.

This more comprehensive of the snowpack significantly improves water supply forecasts critical to water managers in making decisions.

Together with cloud seeding, this technology is helping water managers turn the corner from historical practices to prepare for and adapt to a changing world in the Upper Colorado River Basin.

For more information, visit ColoradoRiverDistrict.org. The “Know Your Snow” webinar is available online at http://www.coloradoriverdistrict.org/events-directory/webinars/.